The present invention relates generally to the field of tandem axle assemblies and, in particular, to an interaxle differential mechanism which, in accordance with the present invention, is provided with a lubricant sump for providing lubricating oil to the differential mechanism during both initial start-up and normal running conditions. The present invention also concerns a unique gear structure which is one component of the interaxle differential. The gear is disk shaped and is provided with integrally formed internal clutch and side gear teeth.
Interaxle differential mechanisms are typically provided in tandem axle assemblies for dividing power from a single drive shaft to two separate axle assemblies. Examples of conventional interaxle differential mechanisms are disclosed in U.S. Pat. Nos. 3,441,106 to Taylor et al. and 2,033,246 to Keese. While tandem axle assemblies having interaxle differential mechanisms have been used for a long time and many various designs have been proposed, there is a continuing effort being made to improve the construction of the interaxle differential in order to reduce its weight and improve its durability and operating characteristics.
For example, the above mentioned Taylor et al patent discloses an interaxle differential construction wherein a side gear of the differential includes external formed side teeth on one side, externally formed clutch teeth on the opposite side engageable with a locking mechanism, and a radial periphery provided with external teeth for transmitting power to one of the two axle differentials. It has been found that this type of structure reduces the number of components in the assembly.
Also, various systems have been proposed for providing lubrication to an interaxle differential, which is typically located in an upper portion of a housing which also encloses one of the two axle differential mechanisms. In this type of arrangement, the interaxle differential is not immersed in the main oil sump, and is typically lubricated by either an auxiliary oil pump or by oil thrown toward the differential by a rotating ring gear. However, such systems generally do not provide sufficient lubrication during initial start up conditions, resulting in undesirable wear of the associated components.
The above mentioned patent to Keese has proposed the use of a separate retaining plate which cooperates with the interaxle differential housing to define an area for retaining a portion of the oil supplied to the interaxle differential mechanism.